Comparative Expression Analyses of Rice and Arabidopsis Phosphate Transporter Families Revealed Their Conserved Roles for the Phosphate Starvation Response

Phosphate is one of the major nutrients of growth, development, and reproduction of crop plants and functions in energy metabolism, signal transduction cascades, and regulates enzymatic activities. To understand uptake and usage of this nutrient in Oryza sativa (rice), a model crop plant, global studies on this family is more effective. Here, we conducted phylogenomic analyses of 26 rice and 19 Arabidopsis phosphate transporters (PHT) reported from previous studies, by integrating various meta-expression data to the phylogenic tree context. Subsequently, of four subfamilies, the PHT1 subfamily was a high affinity phosphate transporter, which functioned under low concentrations of phosphorous in soil, while the others (i.e., PHT2, PHT3, and PHT4) were low-affinity phosphate transporter subfamilies. Most members of the PHT1 in rice and Arabidopsis, in contrast to the other transporter subfamilies, showed significant induction under phosphate starvation, and the responses were more obvious in the roots. These results indicated that the functions of PHT1 phosphate transporters in rice and Arabidopsis were well conserved in response to phosphate starvation. We confirmed significant upregulation of seven PHT1 subfamily genes in rice under phosphate starvation, by RT-PCR, indicating that the high affinity phosphate transporters played important roles in the uptake of phosphate under phosphate deficiency. The regulatory network of OsPT4 belonged to the PHT1 subfamily based on RiceNet analysis, suggesting clues for further analyses. Our study showed the significance of at least seven PHT1 subfamily members, which could improve the efficiency of phosphate use in rice, as a model crop plant.